The exemplary embodiments of the invention relate generally to modem boards for use in wireless telecommunications. In particular, various embodiments are directed to techniques for enhancing the real time performance of operating systems such as SMP Linux with PREEMPT RT for multi-cell support on a single modem board using a multi-core processor. While the invention is particularly directed to the art of wireless telecommunications, and will be thus described with specific reference thereto, it will be appreciated that the invention may have usefulness in other fields and applications.
By way of background, LTE (Long Term Evolution) is a rapidly evolving 3GPP project that aims to improve the UMTS (Universal Mobile Telecommunications System) mobile phone standard to cope with future communication network demands. LTE improves wireless network efficiency and bandwidth, lowers costs, and enhances the service experience. Specifically, LTE makes use of new spectrum opportunities and offers better integration with other open standards. LTE generally includes an LTE RAN (Radio Access Network) (also known as E-UTRAN) along with an EPS (Evolved Packet System, also called Evolved Packet Core).
Communication systems are generally split into two primary functions: data plane functions and control plane functions. In previous LTE products, at least two processors were used on the modem board: one to support the control plane functions (non-real time, e.g., Operations, Administration, and Management (or OA&M), and call processing management-related functionalities), and another to terminate and support the data plane functions (real time, e.g., LTE Layer 2 processing). Both the control and data planes used different operating system (OS) instances, such as Linux for the control plane and a real-time OS such as vXWorks (made and sold by Wind River Systems of Alameda, Calif.) for the data plane core. Typically, one modem board supported one sector or cell. So to support multi-cell (e.g., three cells or six cells) configurations, it would be necessary to provide as many modem boards as the number of cells.
As an improvement, a multi-core processor may be used in an LTE wireless base station on a modem board. In that case, an operating system such as SMP Linux with PREEMPT RT patch runs on one SMP (symmetric multiprocessing) partition that contains all eight cores. In this configuration the control plane (non-real time threads and processes) and the data plane (real time threads and processes) share the same operating system instances even though they are bound to run on different cores.
However, open source SMP Linux with PREEMPT RT is not a hard core real time operating system, such as vxWorks. Therefore, to ensure the optimal real time performance from SMP Linux with PREEMPT RT, a number of techniques may be employed to reduce, or even eliminate, the unbounded latency spikes that typically result from the use of such an operating system. The unbounded latency spikes, if not addressed and eliminated, tend to adversely affect the overall system behavior of applications such as the LTE Layer 2 scheduler, possibly rendering the system incapable of deployment.
Thus, there is a need for a method and system for enhancing the real time performance of an operating system such as SMP Linux with PREEMPT RT patch by, for example, (a) disabling non-essential interrupts on the data plane cores that are dedicated to run only the real time processes or threads and routing these interrupts to the control plane core and (b) running certain hardware components in “polling” mode as opposed to the default “interrupt” mode, thereby reducing the number of interrupts generated for a particular data core.